The present invention is directed to a method of making an impure reaction product containing 2,6-bis(2,4-dihydroxy phenylmethyl)-4-chlorophenol and its use as a polyester cord dip. This product is made by a multistep process without isolating impurities or product. The impure reaction product is referred to herein as 2,6-bis (2,4-dihydroxy phenylmethyl)-4-chlorophenol. The prior art material is possibly also an impure reaction product. The dipped cord is used to reinforce rubber products such as tires.
Cord dips based upon the use of 2,6-bis(2,4-dihydroxy phenylmethyl)-4-chlorophenol are well known. See for example U.S. Pat. Nos. 3,660,202 Edington (1972); 3,857,730 Kalafus et al. (1974) and 3,861,980 Wise (1975); also see an article by Mather entitled "Development of a Polyester Rubber Adhesive," British Polymer Journal, Volume 3, March 1971. These cord dips are very effective and are widely used.
An experimental cord dip possibly based upon 2,6-bis(2,4-dihydroxy phenylmethyl)-4-chlorophenol made by a one-step method without isolation of product or separation of impurities may have been sampled to General Tire by ICI in 1973. The sampled ICI dip however had shortcomings and apparently never became commercial.
The Wise patent discloses the concept of using the 2,6-bis(2,4-dihydroxy phenylmethyl)-4-chlorophenol as made. While the concept is disclosed in the Wise patent, the concept disclosed is actually part of and inseparable from the invention of the present application. The best mode contemplated by the inventors named in U.S. Pat. No. 3,660,202 for making 2,6-bis(2,4-dihydroxy phenylmethyl)-4-chlorophenol is set forth as follows:
768 g. of p-cholorphenol (6.0 moles) was dissolved in 300 g. (7.5 moles) of sodium hydroxide and 1,200 ml. of water. To this solution was added 37 percent aqueous formaldehyde 1,320 ml. (16.6 moles). This solution was maintained in a thermostat bath at 37.degree. C. for 40 hours. The precipitated sodium salt was filtered off, slurried with cold water and refiltered. The sodium salt was then dissolved in water at 90.degree. C., acidified to pH 6.0 with glacial acetic acid, cooled to room temperature and the dimethylol derivative filtered off, and slurried with cold water until acid free. PA1 This product was crystallized from ethyl alcohol and consisted of 2,6-bishydroxymethyl-4-chlorophenol. It had a melting point of 161.degree.-163.degree. C. The dimethylol derivative 2,6-bishydroxymethyl-4-chlorophenol 70 g. (0.375 mole) and resorcinol 124 g. (1.125 moles) were ground together and fused by heating at 150.degree. C. under nitrogen in a polycondensation apparatus for 2 hours. The product was then boiled with water to remove excess resorcinol, filtered hot and dried. The product was a reddish-brown solid comprising 2,6-bis(2',4'-dihydroxy phenylmethyl)-4-chlorophenol. It was a fusible oligomer with a melting temperature of 150.degree.-200.degree. C. and its solubility in 5 normal aqueous ammonia was greater than 20% weight/volume. PA1 a. reacting in the presence of from about 0.05 to 0.8 mole, preferably 0.1 to 0.5, of a base catalyst, PA1 b. then without separating the 2,6-bishydroxymethyl-4-chlorophenol from the reaction mixture, adding PA1 c. heating the mixture to form a reaction product containing 2,6-bis(2,4-dihydroxy phenylmethyl)-4-chlorophenol PA1 d. adding base to the mixture to dissolve the 2,6-bis(2,4-dihydroxy phenylmethyl)-4-chlorophenol and to increase the pH to a value above 7 PA1 e. then without separating the 2,6-bis(2,4-dihydroxy phenylmethyl)-4-chlorophenol from the reaction mixture, adding a major amount by weight on a solids basis of an alkaline dispersion of a rubbery vinyl pyridine copolymer to a minor amount by weight on a solids basis of the reaction product containing 2,6-bis(2,4-dihydroxy phenylmethyl)-4-chlorophenol. The composition produced is a stable alkaline dispersion that can be used directly as a cord dip. Attempts at making cord dips with the prior art 2,6-bis(2,4-dihydroxy phenylmethyl)-4-chlorophenol compositions without isolation from the reaction mixture resulted in unstable dispersions.
Instead of the fusion process, the patent also contemplates a reflux method using large quantities of water with separation of the product.
As can be seen, an excess of formaldehyde is added in the first prior art step. The excess is then removed. The disposal of the removed formaldehyde will result in a disposal or a water pollution problem. The removal of the formaldehyde also results in a time consuming and expensive process step. The same can be said of the salt forming and alcohol crystallization steps. The journal reference suggests eliminating the isolation step of the intermediate but does not suggest how this is to be accomplished. The reflux process of the patent generates even more pollution. Phenolic and formaldehyde pollutants are very difficult if not impossible to remove by sewage treatment and by the water treatment normally used for drinking water supplies. This often results in off-taste and odor in drinking water. The off-taste and odor is carried over even by distillation of the polluted drinking water supply.